This application claims the priority of German Patent Document No. 103 45 748.8, filed Oct. 1, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method of detecting the docking of a vehicle to a docking system.
Particularly in the case of autonomously driven vehicles (that is, vehicles which operate without a driver), such as may be utilized for example in a forwarding company yard, it is necessary to detect the end of a docking operation. When such a vehicle approaches a docking system, such as a loading ramp for loading or unloading, a semitrailer, container or trailer, it is necessary to detect the point in time at which the vehicle is docked, so that the vehicle can be braked in time.
In autonomously driven vehicles, it is known to provide switches which trigger braking when the vehicle comes in contact with a loading ramp. Alternatively, a distance measurement can take place, for example, by means of lasers, and braking can be implemented starting from a certain distance. Additional sensors are required for this purpose, however.
One object of the present invention is to provide a method for detecting docking of a vehicle without requiring additional sensors or switches.
This and other objects and advantages are achieved by the method according to the invention, in which changes in quantities that are indicative of longitudinal velocity of the vehicle and engine torque are monitored. If the change of the velocity quantity is below a defined first value and the change of the engine torque quantity is above a defined second value, it can be determined that a docking has taken place.
The longitudinal velocity a vehicle (or a quantity indicative of it) and the engine torque (or a quantity indicative of it) are detected in all events for other purposes, such as controlling the engine torque. Moreover, temporal changes of the detected quantities can be determined easily, without any additional switches or sensors on the vehicle, in a software module. For this purpose, only the velocity quantity and the engine torque quantity have to be fed to the software module.
When the vehicle comes in contact with a loading ramp, a semitrailer or a trailer, the velocity drops abruptly; and as a result of rotational speed control, the actual engine torque rises simultaneously. Particularly when the change of the engine torque quantity is >>0 and the change of the velocity quantity is <<0, docking is indicated, and braking of the vehicle can be initiated. A Human interaction is not required for braking the vehicle.
In an advantageous variant of the method, automatic braking takes place when a docking is detected. In particular, when a change of the velocity quantity is below the defined first value and a change of the engine torque quantity is above the defined second value, a braking command can given to the braking system and/or the braking can take place by way of the engine. For example, a zero torque can be defined for the engine, or the engine can be returned to its idling rotational speed. Depending on the further development of the transmission line, the clutch can also be opened when a docking is detected. The braking command and the zero torque can be transmitted (via a CAN bus which is already present in the vehicle) to the braking system and the engine control, for example, by a software module which determines whether a docking is taking place.
In a preferred variant of the method according to the invention, the change of the velocity quantity is monitored by reference to the change of rotational wheel speed of at least one vehicle wheel, particularly a rear wheel. As a rule, in the case of vehicles, the longitudinal velocity is determined by measuring a quantity proportional to the longitudinal velocity and correlated therewith. A quantity which is particularly easy to measure is the rotational wheel speed. A change of the rotational wheel speed is accompanied by a change of the longitudinal velocity of the vehicle. Thus, the change of the longitudinal velocity can be determined in a simple manner from the measured rotational wheel speed. However, it may also be provided that the rotational wheel speed is fed directly to the software module and is used to determine whether a docking is taking place.
When the longitudinal velocity of the vehicle is monitored (particularly whether the longitudinal velocity is below a defined velocity value), docking can be detected unambiguously. As a rule, docking is preceded by a maneuvering operation, so that the vehicle drives at a low longitudinal velocity. If a rapid change of the rotational wheel speed and engine torque occurs in such a situation, this is most probably a docking. The detection of a slow longitudinal velocity (particularly a velocity below a threshold value) can be provided as a prerequisite for the detection of the docking. It is conceivable, for example, to determine the changes of the engine torque quantity and of the velocity quantity with respect to time only when the vehicle drives at a longitudinal velocity below the threshold value. In this case, it is advantageous for the longitudinal velocity of the vehicle to be used as the velocity quantity.
It is particularly advantageous to detect and analyze additional vehicle parameters for identifying a docking, particularly vehicle parameters describing the condition of the transmission line. One such parameter which may be used for this purpose is the engaged gear of a transmission, from which the driving direction and the transmission ratio can be detected. It can, for example, be detected whether the reverse gear is engaged. Only then can a docking be involved. The detection of additional vehicle parameters can therefore enhance the reliable detection of the docking. These preferably include the condition of a clutch (engaged or released) situated in the transmission line and the rotational engine speed, from which the rotational input speed and the rotational output speed of the transmission are obtained.
In addition, the object of the invention is achieved by a module to which an engine torque quantity describing the engine torque and a velocity quantity describing the longitudinal velocity of the vehicle are fed, and which has devices for determining change of the engine torque quantity and of the longitudinal velocity quantity, which are connected with devices for determining whether a docking is taking place. Without providing additional sensors on the vehicle, such a module can determine reliably whether a docking of the vehicle to a docking system is taking place, and a braking maneuver can be initiated. The module can be constructed as a hardware module.
As an alternative and preferably, the invention can be constructed as a software module, and the process can be performed by a microprocessor which is otherwise present in the vehicle. The process can thus be implemented and carried out in a particularly cost-effective manner, and no additional hardware is required for detecting the docking.
When additional input quantities describing additional vehicle parameters, such as the velocity or status quantities of the transmission and drive train, are supplied to the module, the decision as to whether a docking has taken place can be based on a more reliable foundation.
In a particularly preferred embodiment, the module is connected by way of a data line, particularly a CAN bus, with the braking system and/or the transmission line control (such as the engine, transmission) of the vehicle. Ordinarily, a CAN bus is present in the vehicle anyway. Thus, no new data lines are necessary for transmitting the braking command. This means that existing autonomously driving vehicles can be retrofitted particularly easily with the module according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.